This invention relates to a conveyor roller assembly particularly intended for use in an aircraft cargo conveying system.
It is well known to provide the floor of the cargo bay of an aircraft with a plurality of rollers aligned with their axes of rotation parallel or substantially parallel to define tracks along which palletised cargo loads (hereinafter known as unit load devices [ULD""s]) are moveably supported by the rollers, the rollers providing a low friction transport for the ULD""s. It is also known to provide similar rollers on one or more inclined loading ramps up and down which ULD""s are transported to and from the cargo bay of the aircraft.
ULD""s typically have a high friction lower surface which engages the rollers, but since the rollers themselves have very little rotational resistance then the ULD""s are relatively free to move, when pushed, or otherwise driven, in a direction at right angles to the rotational axes of the rollers.
It is an object of the present invention to provide a conveyor roller assembly for an aircraft cargo handling system in which control over the speed of movement of ULD""s can be effected. It is a further object of the invention to provide a cargo roller which has a braking torque at a predetermined speed of rotation in one or both directions, but is free to rotate at all speeds below sid predetermined speed in either direction. Where the roller is arranged to provide braking in one rotational direction only, it is free to rotate at all speeds in the opposite direction.
In accordance with the present invention there is provided a conveyor roller assembly comprising a support through which the roller assembly can be fixed in use, a hollow, generally cylindrical roller shell supported for rotation about its longitudinal axis on said support, an electrical generator housed within said roller shell and driven thereby by rotation of the shell to produce an electrical output, a brake within said roller shell and operable to brake rotation of said shell relative to said support, a speed sensor within said shell for sensing the speed of rotation of said shell relative to said support, and, an actuator powered by the electrical output of said generator when said speed sensor detects that the speed of rotation of said shell relative to said support exceeds a predetermined value, to effect operation of said brake to brake rotation of the shell.
Preferably a shock absorbing mechanism is interposed between the roller shell and the drive input of said generator to cushion any sudden speed changes of the roller shell relative to said support.
Conveniently said shock absorbing mechanism comprises first and second components capable of limited relative rotation and resilient means interposed between the components to transmit drive therebetween.
Desirably rotation of said roller shell is transmitted to said generator means through the intermediary of a step-up gearbox within the roller shell.
Preferably said speed sensor is arranged also to determine the direction of rotation of the shell relative to said support whereby said actuator may be actuated by rotation of the roller shell relative to said support in one direction only.
Conveniently said actuator includes an electromechanical mechanism for linking said shell to a brake component rotatable with the shell relative to a stationary brake component with which it makes frictional contact.
Desirably said electromechanical mechanism includes a solenoid and a pawl moved by energisation of the solenoid to link the roller shell to said brake component.
Preferably said speed sensor includes at least one Hall Effect device and one or more permanent magnets movable with said roller shell relative to said device.